This section is intended to provide a background or context to the disclosed embodiments that are recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Accurate reproduction of audio content is an important goal of any audio playback system. To achieve this goal, various high fidelity audio equipment have been developed to process and subsequently reproduce an audio content while preserving and, sometimes, enhancing the characteristics of the original audio content. These efforts for enhancing the listener's audio experience often requires the use of expensive audio processing equipment and multi-channel speaker systems. However, with the increasing popularity of desktop, laptop and portable devices for accessing and playback of music, movies and other multi-media content, high-fidelity reproduction of audio content using relatively inexpensive speaker systems has become more important.
One of the challenges associated with using inexpensive speakers for audio playback relates to the reproduction of the bass components of an audio signal. A bass signal occupies the low-end of the human auditory range (i.e., approximately the frequency range between 20-200 Hz) which often carries important portions of the overall audio content. For example, appreciable portions of a speech signal, and especially those corresponding to male voices, are present in the bass range of frequencies, as well as other bass frequencies in signals from musical instruments and special effects, such as explosions. Inexpensive audio speakers, however, cannot reproduce all of the bass components due to physical limitations. These limitations arise since the speaker transducer dimensions are typically much smaller than the wavelengths associated with the audio base components. To overcome these limitations, high-end speaker systems often utilize sub-woofers that, although more expensive, are physically capable of adequately reproducing the bass content.
Alternative methods have also been developed to improve the sound reproduction quality at the lower end of the audible range without the use of a sub-woofer. One such technique uses a psycho-acoustic phenomenon, known as “the missing fundamental,” to create the perception of hearing low frequencies by generating audio components in a higher frequency range. For example, a listener may still perceive a missing fundamental frequency component of say, 100 Hz, if higher harmonics at say, 200 Hz, 300 Hz, 400 Hz, etc., are present at sufficient amplitudes. As such, a speaker system can create the perception of a bass component by generating the proper higher order harmonics of the bass content.